• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Stromberg ASR-880 Biasing

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Re-reading the entire thread, I like your earlier idea about putting the power resistor in the power supply primary. That sounds like a much better idea than what I said about putting it in the secondary.

As a test I can reduce the line voltage to 117 Volts with a Variac and see what I measure on the DC side.
 
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PRR

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Joined 2003
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> R91 and its Br,R,Gr 1.2M Ohm.

Ah, me wrong, too much squinting. There is a Balance pot and two 150K hung on that. So the string is more like 10K, 5K, 70K, and some others. Given 60V in, about 45V at the grids.

My point remains. If you want the tubes to idle hotter, reduce the to-ground resistor. Try a 1Meg or 500K across the 1.2meg. Get to "a little too hot", then you can trim-back with the trimmer.
 
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